1. Field of the Invention
The present invention is broadly concerned with improved non-explosive actuator assemblies forming a part of hazard suppression apparatus, and complete suppression apparatus of this type. More particularly, the invention pertains to such actuator assemblies including first and second spaced apart rupture discs operable, upon delivery of a charge of high pressure initiator fluid to the zone therebetween, to sequentially rupture and permit full venting of hazard suppression fluid from a container thereof; a perforate support is provided adjacent the face of the second disc remote from the zone in order to prevent premature rupturing of the second disc and assure reliable operation.
2. Description of the Prior Art
Fire or explosion suppression systems typically include a container having a pressurized suppressant which is discharged into a protected area through a nozzle or outlet upon opening of a valve or opening a rupture disc. In the case of rupture discs, opening occurs when the pressure differential across the disc reaches a predetermined amount, known as the set or burst pressure. In a typical application, the pressure on one side of the disc is atmospheric and the set or burst pressure is on the order of 600-700 psig. Selection of material making up the rupture disc, as well as material thickness and disc modifications (e.g., bulging and/or lines of weakness) all influence the burst pressure.
It is also known to provide multiple disc actuator assemblies which are operatively coupled to a source of hazard suppression fluid. In one such design, a pair of spaced apart discs are provided, with the inner disc being perforated so that the zone between the discs is maintained at the same pressure as the fluid container. In order to rupture an assembly of this type, an electrically operated squib or initiator is placed through the sidewall of the actuator between the discs. This squib is provided with a side rupture disc in communication with the zone between the primary discs. In use, when a hazard is detected an electrical signal is sent to the squib which explosively ruptures the side-mounted disc. This in turn causes the imperforate outer disc to rupture, followed by rupturing of the inner perforated disc, i.e., the perforated disc is designed to withstand the pressure pulse generated by the squib long enough to allow burst of the outer imperforate disc.
In some applications however, electrically operated squibs or initiators are discouraged or even prohibited. For example, on oil rigs use of such squibs is considered a safety hazard, owing to the possibility of creating a large-scale explosion upon electrical actuation of the squib. It has been suggested to use other types of actuating mechanism in such cases, such as a source of high pressure inert gas, usually nitrogen. In systems of this type a solenoid valve is opened in response to sensing of a hazard, allowing the high pressure charge to rupture the side disc. However, it has been found that the pressure pulse generated by an inert gas charge differs considerably from that generated by a squib, and that as a consequence the prior multiple disc assemblies will not operate properly. Specifically, the perforate inner disc tends to initially burst causing the high pressure to be diffused into the contents of the fire suppression fluid container, with the result that the total system pressure is not sufficient to burst the outer imperforate. In short, the system fails.
There is accordingly a need in the art for improved pressurized fluid-operated hazard suppression apparatus, and particularly a fluid-type actuator assembly therefor, which assures that the discs of a multiple-disc actuator operate in the proper sequential order so as to assure rapid and reliable delivery of the suppression fluid to a protected area.